Moving bed technology

The discovery (92) that the graphite coating of molecular sieves can dramatically improve their attrition resistance without significantly impairing adsorption performance should allow the extension of moving-bed technology to bulk gas separations (93). 

Gattuso M. J., McCulloch B., House D. W., Baumann W. M., Gottschall K. (1996) Simulated Moving Bed Technology - The Preparation of Single Enantiomer Drugs, Pharm. Tech. Europe 8 20-25. 

Several technological variations for cracking operations were developed over the years. The fixed-bed and moving-bed technologies have been largely replaced... 

D.B. Broughton, Production scale adsorption of liquid mixtures by simulated moving bed technology, Sep. ScL Technol. 19, 723-736 (1984-1985). 

This process could cope with gasoline demand by only steadily improving the catalyst stability. Nevertheless, this process would reach its limits if process technology would remain unchanged. Consequently, moving bed technology, which allows continuous or semicontinuous regeneration of the catalyst, was developed. 

Kearney, M., Simulated Moving-bed Technology Applied to Chromatographic Recovery of Sucrose from Sucrose Syrups, Proc. Sugar Processing Research Conf, 291-304, 1990. 

Various processes have been devdoped by Chevron, ShelL Sinclair, Southern Petro-chemical, etc., and particularly by ICJ Imperial Chemical Industries Maruzen (XIS processX which operates in the presence of steam at a ratio of 0.05 to 0.15 mol/mol of xylenes feedstock, and ARCO, which proposes the permanent regeneration of its catalyst by using the moving bed technology. These processes are usually combined with a p-xylcne recovery technique, generally by crystaDizatioa The isomerization yield depends on the ethylbenzene content at the reactor inlet and on the desired target product, either p-xylene alone or o- and p-xylenes simultaneously.. . ... 

If all these factors are fulfilled, quite reasonable productivity rates can be achieved. Most separations described so far have been performed in the conventional batch-mode process however, there is growing interest in simulated moving-bed technology, as... 

In recent years, enantioselective chromatography was extended to semipreparative separations and now simulated moving-bed technology (SMB) has become available for the resolution of some synthetic racemates in preparative scale. In the pharmaceutical industry this progress is of considerable interest with respect to enantiopure drug applications. 

Wongso, F., Hidajat, K. and Ray, A. K. (2004). Optimal operating mode for enantioseparation of SB-553261 racemate based on simulated moving bed technology, Biotechnol. Bioeng., 87, pp. 714-722. 

In a recent paper Grasselli et al [12] have proposed a mechanism with activated O2-(peroxo) species on unsaturated V ion at the surface and have proposed that the active site is composed of an ensemble of four dimers isolated one from the other by excess of phosphate species as schematised in fig. 2. Note that if such an assumption is true it is hard to understand how such activated oxygen species may be stable at high temperature and to understand the moving bed technology recently developed by the Dupont researchers [13]. In the later case one can expect surface oxygen species to be consumed and thus the ratio value to... 

In the Arco technique, conversion takes place in the absence of hydrogen, at a pressure dose to atmospheric conditions (0i2.10 Pa absolute) and a temperature that rises gradually during the run from 480 to 520°C. Subsequently, the catalyst, similar to those employed iu catalytic cracking, which is a modified sifica-alnmina (mordenite doped with nickel) without noble metal, is rapidly poisoned by the coke, and must therefore be regenerated frequently. The moving bed technology is therefore employed. 

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